| In recent years,the rapid development of electromagnetic technology,for the convenience of people at the same time,but also derived from a series of problems such as electromagnetic radiation and electromagnetic interference,not only endanger human health,but also to the military and other important areas constitute a serious threat,metamaterial absorbers as an effective device to solve the above problems and has been widely studied and applied.As a new type of multifunctional solvent and soft material,imidazole-like ionic liquid shows excellent physicochemical properties and dielectric properties,and is a new type of soft medium absorbing material with great development significance.Based on the high loss characteristics and temperature sensitivity of imidazole-like ionic liquids,the ionic liquid named 1-ethyl-3-methylimidazolium dicyanamide salt（[EMIM][N（CN）2]）is selected in this thesis to design and prepare ionic liquid-based monocyclic ultra-broadband absorbers,thermally tunable broadband absorbers and fully dielectric thermally tunable absorbers in the microwave band,and the main work is as follows:In this thesis,an imidazole ionic liquid based single-loop ultra-wideband absorber has been simulated and constructed.The absorber has achieved an ultra-wideband absorption rate greater than 90%and a relative bandwidth of 121.29%in the microwave frequency range of 12.25-50GHz.The highly symmetric structural characteristics of the single-loop absorber make it have the characteristics of wide incidence angle,arbitrary polarization angle and temperature insensitivity,simultaneously.In addition,based on the impedance matching principle,the influence law of the dielectric surface material of the single-loop absorber on the absorption of electromagnetic waves is studied,and the loss mechanism of electromagnetic waves in the absorber at the resonance peak is further analyzed from the perspectives of loss attenuation and electromagnetic field vector distribution.Finally,the ultra-wideband absorption capacity of the absorber is verified by experiments.The influence law of temperature on ionic liquid based wideband metamaterial absorber is explored.It is found that the absorber realizes the effect that the absorption rate of low frequency decreases with the increase of temperature and the absorption rate of high frequency increases with the increase of temperature in the range of 20-100℃.Moreover,the absorber has the capability of broadband absorption in the frequency range of 23.5-48GHz.In addition,the thermally adjustable absorbing mechanism in 2-10GHz and 35-48GHz frequency bands is explained in detail from the perspective of energy loss.At the same time in TM and TE mode,the thermal adjustable absorber has the characteristics of wide incidence Angle below 30°and polarization Angle between 0°and 90°.In order to further expand the application field of the absorber,an all-dielectric thermal adjustable broadband absorber is proposed and constructed.The simulation and experimental results show that the absorber has the effect of increasing the absorption rate with the temperature when the metal plate is removed.Up to 100℃,the absorber achieves broadband absorption in the frequency band range of 20-50GHz,and the absorption bandwidth reaches 30GHz.Based on the distribution law of electromagnetic loss at the resonance peak,the absorption performance of the absorber is analyzed with temperature,and it is found that the energy loss is mainly concentrated in the middle and upper regions of the ionic liquid,and the area of the loss region increases with the increase of temperature,and The loss intensity increases gradually with the increase of temperature and reaches the peak at 100℃,which corresponds to the increase of absorption bandwidth with the increase of temperature.Finally,the electromagnetic performance of the absorber is tested based on the free-space method,and the experimental and simulation results are consistent. |
